Turn diagnostic mode selector on ECU to On position and wait until
inspection lamps flash.

Note number of flashes, then immediately turn diagnostic mode selector
to Off position.

On all models, when ignition is turned Off during diagnosis, in each
mode, and then turned back On again after power to the ECU has dropped off
completely, diagnosis will automatically return to Mode I.

For description of modes, proceed as follows:

Mode I (Mixture ratio feedback control monitor A): during a closed
loop condition, the green inspection lamp turns on when lean condition
is present and goes off when a rich condition is present. During an
open loop condition, the green inspection lamp stays off.

Mode II (Mixture ratio feedback control monitor B): during a closed
loop condition, the red inspection lamp turns on and off simultaneously
with the green inspection lamp when mixture ratio is controlled within
a predetermined value. During an open loop condition, the red inspection
lamp stays off. The green inspection lamp function is the same as in
Mode I.

Mode III (Self diagnosis): in this mode the DTC is indicated by both
the red and greed inspection lamp. The red inspection lamp corresponds
to units of 10; the green inspection lamp corresponds to units of one.

Mode V (Real time diagnosis): if a malfunction is present during
a driving test, the inspection lamps will display the malfunction condition
immediately.

READING DIAGNOSTIC CODES

The Electronic Control Unit (ECU) monitors several engine sensors and actuators.
If a problem occurs the information is stored in the ECU’s memory for retrieval.
The codes are displayed by the red diode on the ECU. The codes are interpreted
by the number of times and duration the diode flashes.
The red diode will flash for 0.6 of a second with 0.6 of a second delay between
flashes “X” number of times, this will represent units of ten.
Then there will be a delay 0.9 of a second and the red diode will flash for
0.3 of a second with 0.3 of a second delay between flashes “X” number of times,
this will represent units of one.
There will be a delay of 2.1 seconds between codes.
For example, if the red diode flashes once and then flashes twice rapidly this
should be interpreted as code 12. The codes are displayed in numerical order
starting with the lowest and ending with the highest.

Nissan UD Diesel

The trouble codes will be displayed by the flashing Engine
Control Lamp and the Overheat Warning Lamp and the Overheat Warning Buzzer.

Trouble Code Interpretation

MID-TICS System

The diagnostic trouble codes will be displayed by the check engine lamp. For
example, a code 12 will be displayed by the check engine lamp flashing 1 time
for approximately 1.2 seconds, followed by a .6 second pause, then 2 short
flashes. Each trouble code will be displayed 3 times before the next trouble
code is displayed.

Clearing Trouble Codes

88-94

Turn the ignition key on.

Turn the diagnostic mode selector on the ECU fully clockwise and wait
more than two seconds then turn the selector fully counterclockwise. The
ECCS system is now in mode 2.

Turn the diagnostic mode selector on the ECU fully clockwise and wait
more than two seconds then turn the selector fully counterclockwise. The
ECCS system is now in mode 1. ECU memory is now erased.